title: In vivo evidence for a significant role of folylpolyglutamate synthase in combined chemotherapy with oral fluoropyrimidine, UFT or S-1, and leucovorin.
abstract: Combined chemotherapy with 5-fluorouracil and leucovorin (LV) has been widely used for the treatment of patients with colorectal cancer. Given that LV effects are attributable to increased levels of reduced folate in cancer cells, we attempted here to show the in vivo role of folylpolyglutamate synthetase (FPGS), which stabilizes intracellular reduced folate, in the anticancer activities of oral fluoropyrimidines, UFT or S-1, combined with LV. To this end, HCT-15 human colon cancer cells were knocked down for FPGS expression by RNA interference. The cell line stably expressing FPGS shRNA (FPGS shRNA HCT-15) was cloned and transferred subcutaneously into nude mice fed a low-folate diet. FPGS shRNA HCT-15 tumors expressed a significantly lower level of FPGS at protein and mRNA levels than parental HCT-15 cells, and the levels of reduced folate in FPGS shRNA HCT-15 tumors became 57% of those in parent after a single administration of 10 mg/kg of LV. Notably, FPGS downregulation did not affect the tumor growth or sensitivity to fluoropyrimidine. Importantly, we observed that LV given for 14 days failed to enhance the anticancer effects of UFT and S-1 in FPGS shRNA HCT-15. This was in keeping with the results that LV did not increase the ternary complex of TS, FdUMP and reduced folate. In conclusion, the present results provide in vivo evidence that intratumor FPGS plays an important role in the efficacy of oral fluoropyrimidine plus LV therapy for colorectal cancer.
authors.affiliation: Tokushima Research Center, Taiho Pharmaceutical Co., Ltd, 224-2 Hiraishi-ebisuno Kawauchi-cho, Tokushima 771-0194, Japan. s-tsukioka@taiho.co.jp
authors.forename: Sayaka
authors.initials: S
authors.lastname: Tsukioka
authors.forename: Etsuko
authors.initials: E
authors.lastname: Sakamoto
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tsujimoto
authors.forename: Fumio
authors.initials: F
authors.lastname: Nakagawa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Saito
authors.forename: Junji
authors.initials: J
authors.lastname: Uchida
authors.forename: Mamoru
authors.initials: M
authors.lastname: Kiniwa
authors.forename: Masakazu
authors.initials: M
authors.lastname: Fukushima
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000201:enzymology*; D015536:Down-Regulation / Q000235:genetics; D005472:Fluorouracil / Q000008:administration & dosage; D005492:Folic Acid / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D002955:Leucovorin / Q000008:administration & dosage; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D010453:Peptide Synthases / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D034741:RNA, Small Interfering; D005492:Folic Acid; D010453:Peptide Synthases; C023103:folylpolyglutamate synthetase; D002955:Leucovorin; D005472:Fluorouracil